I would agree that all the passages cited so far are just beautiful.  If I had to think of another one, though, I would add the meeting of Thingol and Melian:

She spoke no word; but being filled with love Elwe came to her and took her hand, and straightway a spell was laid on him, so that they stood thus while long years were measured by the wheeling stars above them; and the trees of Nan Elmoth grew tall and dark before they spoke any word.

I've always found the juxtaposition of time and timelessness in this scene very striking -- I can see it as a movie scene, with the lovers being still and the world around them sped up.  I also think it captures the feeling of being amazed by love, as if the world stops and you are entranced... For me, this passage fits the description of Tolkien's writing so beautifully expressed by Luthien Rising in her post below:  it's "both fully human and more than human, bringing the mythic home."

The Reading Room

Oooo...another great book on philology!